Response surface optimization of extraction of rutin and quercetin from Cyclobalanopsis leaves by hydrothermal treatment catalyzed by ethanol-acetic acid

An environment-friendly hydrothermal method was developed to extract rutin and quercetin from a forestry waste of Cyclobalanopsis leaves using the mixture medium of alcohol-acetic acid–water. Various process variables were specifically studied, which included the concentration of acetic acid (0 ~ 40% v/v), ethanol content (30 ~ 80% v/v), reaction temperature (100 ~ 200 ℃), liquid–solid ratio (10 ~ 50 mL/g), and reaction time (1 ~ 7 h). The optimal combination of extraction parameters was established using single factor experiments and the 3 × 3 Box-Behnken design (BBD), which is a response surface methodology (RSM) with acetic acid concentration and time set to 15% (v/v) and 5 h, respectively. Optimal extraction conditions of rutin were the ethanol concentration of 57% v/v, the temperature of 183℃, and the liquid–solid ratio of 36 mL/g. Under these conditions, the average experimental yield of rutin was 155.36 mg/g. Optimal conditions of quercetin were the ethanol concentration of 60% v/v, the temperature of 180℃, and the liquid–solid ratio of 23 mL/g, which resulted in the highest yield of quercetin of 32.39 mg/g. Compared with the conventional reflux extraction (the yields of rutin and quercetin were 51.11 mg/g and 6.67 mg/g, respectively), the hydrothermal treatment was significantly beneficial to the extraction of rutin and quercetin.